FDD/CDMA transmission/reception system

ABSTRACT

An FDD/CDMA transmission/reception system includes a CDMA transmitter and a CDMA receiver. The CDMA transmitter includes a plurality of transmission antennas, signal transmission units for transmitting transmission signals weighted by different values to the respective transmission antennas, and pilot signal transmission units for transmitting a plurality of different pilot signals to the respective transmission antennas. The CDMA receiver includes a reception unit for obtaining one received signal from the transmission signals from the plurality of transmission antennas of the CDMA transmitter in consideration of reception quality, and a unit for transmitting antenna control signals corresponding to reception power values of the received pilot signals to the CDMA transmitter.

This is a continuation of application Ser. No. 08/683,675, filed Jul.17, 1996 now U.S. Pat. No. 5,886,987.

BACKGROUND OF THE INVENTION

The present invention relates to a CDMA (Code Division Multiple Access)transmission/reception system and, more particularly, to a CDMAtransmission/reception system generally used for a forward link(communication from a base station to a mobile state) in a mobilecommunication system.

A code division multiple access (CDMA) scheme based on a direct spreadtechnique has received a great deal of attention as a multiple accessscheme in a future mobile communication system. This is because the CDMAscheme has the potential for a great increase in subscriber capacity. Ina system using the CDMA scheme, each user multiplies information signalby a unique spread code to spread the signal into a signal in a widefrequency band, and transmits the resultant signal to a transmissionchannel. On the reception side, the code multiple signal undergoes ade-spread process, and the desired user signal is detected afterward.

FIGS. 11A and 11B show a conventional CDMA transmission/receptionsystem. FIG. 11A shows a transmitter. FIG. 11B shows a receiver. In thistransmission/reception system, the transmitter multiplexes user signalsto receivers, i.e., mobile stations, altogether. In the transmitter, theuser signals and pilot signals are multiplexed to allow the receiver toeasily estimate the reception timings of the respective user signals andtransmission channel parameters.

Referring to FIG. 11A, in the transmitter, user signal spreadingcircuits 501-1 to 501-K (K is an integer not less than 1; the sameapplies to the following description) spread the respective user signalswith unique codes assigned to the respective users. A pilot signalspreading circuit 502 spreads a pilot signal with a unique code. Asignal combiner 503 multiplexes the spread user signals supplied fromthe user signal spreading circuits 501-1 to 501-K and the pilot signalfrom the pilot signal spreading circuit 502. A transmission antenna 504transmits an output from the combiner 503.

Referring to FIG. 11B, in the receiver, a pilot correlator 601 detectsthe pilot signal from the received signal transmitted from thetransmission antenna 504 and received by a reception antenna (notshown), and extracts the reception timings of the user signals andtransmission channel parameters. Similarly, a user signal correlator 602detects a desired user signal from the received signal. A coherentdetector 603 demodulates a user signal by using the transmission channelparameters extracted from the pilot signal. Note that illustrations ofan RF (radio frequency) transmitter and a receiver are omitted fromFIGS. 11A and 11B.

In a mobile communication environment, fading caused in a transmissionchannel generally becomes a factor for a deterioration in receptionquality. As a means for improving the reception quality in a fadingenvironment, for example, an antenna diversity scheme is effective,which is disclosed in Japanese Patent Application No. 6-189293 (Title ofthe Invention: “Code Division Multiple Receiver”) which is a pendingapplication filed by the present applicant. This scheme is a selectionscheme in which a plurality of antennas are arranged in a receiver tohave independent spatial correlation characteristics, and a signalhaving good quality is selected from signals received by the antennas,or a combining scheme in which signals are appropriately weighted andcombined. With the use of such a scheme, the reception characteristicsin a fading environment can be improved. However, it is difficult toapply the scheme to a mobile station, because a complicated apparatus isrequired.

In the CDMA transmission/reception system shown in FIGS. 11A and 11B, indetecting a desired signal, interference occurs owing to the correlationbetween the desired user code and other users codes. Variousinterference cancellation schemes have been proposed (e.g., JapanesePatent Laid-Open No. 7-030519) to cancel such interference in a receiverand attain high reception quality. However, it is not easy to apply aninterference canceler to a mobile station, considering a shortage ofinformation associated with other users and the apparatus size.Therefore, there is a demand for a means for obtaining an interferencereduction effect without applying an interference canceler to a mobilestation.

In order to meet this demand, there has recently been proposed a schemeof obtaining a diversity effect and an interference reduction effectwithout using a plurality of antennas and an interference canceler in amobile station. This scheme is disclosed in Miya, Hayashi, Kato, andHomma, “A Base-Station-Based Diversity Scheme for CDMA/TDD Systems”,TECHNICAL REPORT OF IEICE. RCS94-73, September 1994. The scheme isapplied to a TDD (Time Division Duplex) scheme, i.e., a scheme in whichcommunication is performed by time division of the same radio frequencyin transmission and reception, and the same transmission channel is usedfor transmission and reception. In a base station, antenna diversity isperformed in a reverse link, and forward link transmission is performedthrough an antenna exhibiting the most effective receptioncharacteristics. With this operation, a diversity effect can be obtainedin a mobile station without using a plurality of antennas.

In the CDMA scheme, with the user of such a transmission diversityscheme, an interference reduction effect can be expected for thefollowing reason. A desired signal is always transmitted through anoptimal transmission channel, whereas a signal of another users, i.e.,interference, is not always transmitted through an optimal transmissionchannel for the desired user. A decrease in interference power can beattained unlike the case wherein all user signals are transmitted from asingle antenna as shown in FIGS. 11A and 11B.

As has been described above, in the conventional CDMAtransmission/reception system shown in FIGS. 11A and 11B, a complicatedmobile station is required to improve the fading and interferenceresistance characteristics. Although there are some merits in the methodof performing transmission diversity using the TDD scheme, a complicatedsystem is required because synchronization in transmission and receptionmust be established between base stations.

In contrast to this TDD scheme, an FDD (Frequency Division Duplex)scheme allows a simple system. In this scheme, different radiofrequencies are used in transmission and reception. A demand thereforearises for a means for obtaining the above effect in the FDD scheme.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide anFDD/CDMA transmission/reception system which can realize transmissiondiversity in the FDD/CDMA scheme and improve fading and interferenceresistance characteristics.

In order to achieve the above object, according to the presentinvention, there is provided an FDD/CDMA transmission/reception systemcomprising a CDMA transmitter and a CDMA receiver, the CDMA transmitterincluding a plurality of transmission antennas, signal transmissionmeans for transmitting transmission signals weighted by different valuesto the respective transmission antennas, and pilot signal transmissionmeans for transmitting a plurality of different pilot signals to therespective transmission antennas, and the CDMA receiver includingreception means for obtaining one received signal from the transmissionsignals from the plurality of transmission antennas of the CDMAtransmitter in consideration of reception quality, and means fortransmitting antenna control signals corresponding to reception powervalues of the received pilot signals to the CDMA transmitter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the arrangement of an embodiment of aCDMA transmitter in a CDMA transmission/reception system of the presentinvention;

FIG. 2 is a block diagram showing the arrangement of an embodiment of aCDMA receiver in the CDMA transmission/reception system of the presentinvention;

FIGS. 3A and 3B are block diagrams each showing an example of thearrangement of an antenna selecting/weighting circuit;

FIGS. 4A and 4B are block diagrams each showing an example of thearrangement of a user signal selecting/combining circuit;

FIG. 5 is a block diagram showing the arrangement of another embodimentof the CDMA transmitter in the CDMA transmission/reception system of thepresent invention;

FIG. 6 is a block diagram showing the arrangement of another embodimentof the CDMA receiver in the CDMA transmission/reception system of thepresent invention;

FIG. 7 is a block diagram showing the arrangement of still anotherembodiment of the CDMA transmitter in the CDMA transmission/receptionsystem of the present invention;

FIG. 8 is a block diagram showing the arrangement of still anotherembodiment of the CDMA receiver in the CDMA transmission/receptionsystem of the present invention;

FIG. 9 is a block diagram showing the arrangement of still anotherembodiment of the CDMA transmitter in the CDMA transmission/receptionsystem of the present invention;

FIG. 10 is a block diagram showing the arrangement of still anotherembodiment of the CDMA receiver in the CDMA transmission/receptionsystem of the present invention; and

FIGS. 11A and 11B are block diagrams showing the arrangement of aconventional CDMA transmission/reception system, in which FIG. 11A showsthe arrangement of a transmitter, and FIG. 11B shows the arrangement ofa receiver.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be described below with reference to theaccompanying drawings.

FIG. 1 shows the arrangement of a CDMA transmitter TR in a CDMAtransmission/reception system according to an embodiment of the presentinvention. FIG. 2 shows the arrangement of a CDMA receiver RV in theCDMA transmission/reception system of the present invention.

Referring to FIG. 1, in the transmitter TR, user signal spreadingcircuits 101-1 to 101-K respectively spread user signals 10-1 to 10-Kfrom K stations with unique codes assigned to the respective users.Antenna selecting/weighting circuits 103-1 to 103-K select transmissionantennas from N antennas 107-1 to 107-N for the respective users byusing antenna selection signals or weighting signals obtained for therespective users, or weight the signals and transmit the resultantsignals to the antennas 107-1 to 107-N.

FIGS. 3A and 3B show the arrangement of the antenna selecting/weightingcircuit 103. FIG. 3A shows an antenna selection scheme using an antennaselection signal. FIG. 3B shows a scheme using a weighting circuit 103-i(i=1 to K).

In the antenna selection scheme in FIG. 3A, a selecting circuit 103Adetermines, on the basis of an antenna selection signal, a specificsignal combiner to which a signal from each spreading circuit is to beoutput.

In the weighting scheme in FIG. 3B, for a signal from each spreadingcircuit, weights 1, 2, . . . , N are respectively assigned to arithmeticunits 103 a, 103 b, . . . , 103 n in a weighting circuit 103B on thebasis of an antenna weighting signal. The resultant signals are outputto signal combiners 105-1, 105-2, . . . , 105-N. Note that the antennaselection scheme is a modification of the weighting scheme, and can beregarded as a scheme of performing a weighting operation to output asignal from each spreading circuit to only one signal combiner(antenna). In other words, a signal with a weight “1” is output to onlyone signal combiner, while a signal with a weight “0” is output to eachof the remaining signal combiners (transmission antennas) to which nooutputs are sent.

In the combining scheme, a user signal to an antenna for a goodtransmission channel is multiplied by a large weight, whereas a usersignal to an antenna for a poor transmission channel is multiplied by asmall weight.

Referring back to FIG. 1, pilot signal spreading circuits 104-1 to 104-N(N is an integer not less than two; the same applies to the followingdescription) respectively spread pilot signals 40-1 to 40-N for theantennas 107-1 to 107-N with unique codes assigned to the respectivespreading circuits. The signal combiners 105-1, 105-2, . . . , 105-N addoutputs from the antenna selecting/weighting circuits 103-1 to 103-K tooutputs from the pilot signal spreading circuits 104-1 to 104-N. Delayunits 106-1 to 106-N respectively delay outputs from the signalcombiners 105-1, 105-2, . . . , 105-N to set different transmissiontimings of signals from the antennas 107-1 to 107-N. The purpose of thisoperation is to separate the user signals transmitted from the antennas107-1 to 107-N along the time axis to allow easy identification of theantennas from which the respective signals are transmitted. The delayamounts in the delay units 106-1 to 106-N are preferably set to severalchip periods, assuming that a timing variation between antennas 107-1 to107-N is larger than a delay dispersion of transmission channels and isregarded as a time shorter than a one-symbol period of a user signal.The antennas 107-1 to 107-N transmit the outputs from the delay units106-1 to 106-N.

Referring to FIG. 2, in the receiver RV, pilot correlators 201-1 to201-N detect pilot signals corresponding to transmission antennas from areceived signal obtained from one reception antenna 200, and extractreception timings corresponding to radio waves from the respectivetransmission antennas and transmission channel parameters. A user signalcorrelator 202 detects desired user signals from the received signalsobtained from the reception antenna 200 at the respective receptiontimings. In this case, the user signals are separated from each otheralong the time axis in accordance with the transmission timings of thesignals from the transmission antennas.

The problem in the selection scheme, in particular, is that thetransmission antenna from which a user signal has been transmittedcannot be accurately identified on the receiver RV. Although an antennaselection signal is detected by the receiver RV, no user signal may betransmitted from an antenna identified by the receiver RV when an erroris caused in information when it is transmitted through a differentline.

For this reason, the receiver RV must estimate, by itself, atransmission antenna from which a user signal has been transmitted. Inthis embodiment, user signals are detected in correspondence with allthe transmission antennas from which a user signal has been possiblytransmitted, and a demodulated signal from the transmission antenna fromwhich the user signal has been transmitted most possibly is used.Detectors 203-1 to 203-N detect user signals at reception timingscorresponding to the respective transmission antennas by usingtransmission channel parameters output from the pilot correlators 201-1to 201-N, and obtain N outputs. A user signal selecting/combiningcircuit 204 selects the most likely output from the outputs from theuser signal correlator 202 and the outputs from the detectors 203-1 to203-N, or combines these outputs to obtain a user signal.

Each of FIGS. 4A and 4B shows an example of the user signalselecting/combining circuit 204. FIG. 4A shows an arrangement for theselection scheme. Referring to FIG. 4A, for example, the signal qualitydetecting circuit 211 receives outputs from the user signal correlator202, obtains the symbol powers of output values at reception timingscorresponding to the respective antennas, and adds up the powerscorresponding to an antenna control period. In this case, since nooutput appears at the reception timing of a radio wave from atransmission antenna from which no signal has been transmitted, atransmission antenna can be specified by selecting the maximum detectedvalue (the maximum reception power value) of these detected values.

Letting I_(N) and Q_(N) be quadrature signal outputs atreception-timings corresponding to transmission antennas and output fromthe user signal correlator 202, an output d_(N) from a signal qualitydetecting circuit 211 is given by

d _(N)=Σ(I _(N) ² +Q _(N) ²)  (1)

In equation (1), Σ is the number of symbols included in an antennacontrol period. If outputs from the detectors 203-1 to 203-N are used,coherent detection can be performed.

Letting I_(N) and Q_(N) be the quadrature signal outputs from thedetector 203-N, an output d_(N) from the signal quality detectingcircuit 211 is given by

d _(N)=Σ(|I _(N) |+|Q _(N)|)  (2)

In equation (2), E is the number of symbols included in an antennacontrol period. A selecting circuit 212 selects one of the outputs fromthe detectors 203-1 to 203-N as a user signal on the basis of the outputd_(N).

In the arrangement for the combining scheme, shown in FIG. 4B, since aweighting operation has already been performed by the transmitter,outputs from the detectors 203-1 to 203-N are directly combined by asignal combiner 212 a to obtain a demodulated signal (user signal).

Power measurement circuits 205-1 to 205-N in FIG. 2 respectively measureoutputs from the pilot correlators 201-1 to 201-N. An antennaselecting/weighting signal detecting circuit 206 detects antenna signalsfrom outputs from the power measurement circuits 205-1 to 205-N, orantenna weighting signals from outputs from the power measurementcircuits 205-1 to 205-N and the detectors 203-1 to 203-N. For example,in the antenna selection scheme, a transmission antenna corresponding toa pilot signal having the maximum power of the outputs from the powermeasurement circuits 205-1 to 205-N is selected.

In the combining scheme, weights are obtained from the outputs from thepower measurement circuits 205-1 to 205-N and directly transmitted.Alternatively, comparison data of weights obtained from the outputs fromthe power measurement circuits 205-1 to 205-N and weights obtained fromthe outputs from the detectors 203-1 to 203-N and actually used in thetransmitter TR may be transmitted. In the combining scheme, it isdifficult to transmit weighting information from the receiver to thetransmitter in a relatively small amount, and complicated control isrequired.

An output from the antenna selecting/weighting signal detecting circuit206, i.e., an antenna selection/weighting signal is sent to atransmission section 300 and transmitted to the transmitter TR via thereception antenna 200. FIG. 2 shows only a portion of the receiver RVwhich is associated with the present invention, but the remainingportion which is not directly associated with the present invention isomitted. Note that since the FDD scheme is used in this case, differentradio frequencies are used for transmission and reception. This FDDscheme is known.

In this embodiment, an antenna selection signal or weighting signal usedin the transmitter TR must be detected by the receiver RV andtransmitted from the receiver RV to the transmitter TR via a link(reverse link) different from a link used to transmit a user signal. Forthis reason, there is a delay between the instant at which an antennacontrol signal is detected by the receiver RV and the instant at whichthe signal is transmitted to the transmitter TR and antenna control isperformed. This delay is generally two to three times an antenna controlperiod. If a fading path variation is fast, a change in transmissionchannel occurs during this delay period, resulting in erroneous antennacontrol. Since the transmission channel variation speed is proportionalto the speed of a mobile station, a diversity effect and an interferencereduction effect can be expected in a low-speed mobile station, but sucheffects cannot be expected in a high-speed mobile station. Antennacontrol can be properly performed in environments in which low-speedmobile stations are mainly present, e.g., microcell and indoor systems.However, in a microcell system in which high-speed mobile stations makeup a large proportion, reception quality varies depending on mobilestations. In this case, by performing transmission power control foreach mobile station, constant reception quality can be maintained in allthe mobile stations, and the overall interference amount of the systemcan be optimized.

Another embodiment of the CDMA transmission/reception system of thepresent invention will be described with reference to FIGS. 5 and 6.

FIG. 5 shows the arrangement of another embodiment of the CDMAtransmitter in the CDMA transmission/reception system of the presentinvention. FIG. 6 shows the arrangement of another embodiment of theCDMA receiver in the CDMA transmission/reception system of the presentinvention. The same reference numerals in FIGS. 5 and 6 denote the sameparts as in FIGS. 1 and 2.

The arrangements in FIGS. 5 and 6 are the same as those in FIGS. 1 and 2except for the addition of an arrangement for controlling transmissionpower.

Referring to FIG. 5, in a transmitter TR, power control circuits 102-1to 102-K respectively receive outputs from user signal spreadingcircuits 101-1 to 101-K, and control transmission power for each usersignal by using a power control signal obtained for each user. Outputsfrom the power control circuits 102-1 to 102-K are supplied to antennaselecting/weighting circuits 103-1 to 103-K.

Referring to FIG. 6, in a receiver RV, a power control signal detectingcircuit 207 receives an output from a user signal selecting/combiningcircuit 204, and detects a power control signal on the basis of, e.g.,desired signal-to-interference power measurement. It suffices iftransmission power control used in this case is performed to control theaverage value of reception levels. In addition, the response speed ofthis control may be low as compared with an antenna control period.Various desired signal-to-interference power measurement methods areavailable. For example, U.S. Pat. No. 4,835,790 discloses a scheme in“Carrier-to-Noise Detector for Digital Transmission Systems”. The powercontrol signal is transmitted from the receiver RV to the transmitter TRvia a link (reverse link) different from a link used to transmit a usersignal.

Still another embodiment of the CDMA transmission/reception system ofthe present invention will be described with reference to FIGS. 7 and 8.

FIG. 7 shows the arrangement of still another embodiment of the CDMAtransmitter in the CDMA transmission/reception system of the presentinvention. FIG. 8 shows the arrangement of still another embodiment ofthe CDMA receiver in the CDMA transmission/reception system of thepresent invention. The same reference numerals in FIGS. 7 and 8 denotethe same parts as in FIGS. 1 to 6.

This embodiment is a modification of the embodiment shown in FIGS. 5 and6. The essential idea of this embodiment is based on the embodimentshown in FIGS. 5 and 6. In the embodiment shown in FIGS. 7 and 8, thedelay units 106-1 to 106-N in FIG. 1 are omitted, and user signals arenot separated along the time axis in correspondence with thetransmission antennas in an output from a user signal correlator 202.For this reason, in the arrangement shown in FIGS. 5 and 6, a correctoutput can be obtained only from a transmission channel having undergoneproper compensation processing, and the remaining outputs are not 0 butare multiplied by erroneous transmission channel parameters, unlike inthe arrangement shown in FIGS. 1 and 2, in which outputs from thedetectors 203-1 to 203-N are set to almost 0 except for a correct one.In this embodiment, therefore, identification cannot be performed by thesignal quality detecting circuit 211 indicated by equation (1), but canbe performed by the method indicated by equation (2).

In the embodiment shown in FIGS. 7 and 8, pilot signals are used fordetection. If, however, a pilot symbol is inserted in each user signalon the time axis in advance, and the receiver performs detection byusing such a signal (Sampei, “Rayleigh Fading Compensation Method for16QAM MODEM in Digital Land Mobile Radio Systems”, THE TRANSACTIONS OFTHE INSTITUTE OF ELECTRONICS, INFORMATION AND COMMUNICATION ENGINEERS,B-II, Vol. J72-B-II, No. 1, January 1989), the user signal selectingcircuit can be omitted. However, even if a pilot signal having a highintensity is transmitted, the signal is not used, which is notpreferable in terms of detection characteristics and transmissionefficiency. As is apparent, the embodiment shown in FIGS. 7 and 8 mayuse a scheme of using different codes in user signals for the respectiveantennas as in the case of pilot signals.

Still another embodiment of the CDMA transmission/reception system ofthe present invention will be described with reference to FIGS. 9 and10.

FIG. 9 shows the arrangement of still another embodiment of the CDMAtransmitter in the CDMA transmission/reception system of the presentinvention. FIG. 10 shows the arrangement of still another embodiment ofthe CDMA receiver in the CDMA transmission/reception system of thepresent invention. The same reference numerals in FIGS. FIGS. 9 and 10denote the same parts as in FIGS. 1 to 8.

This embodiment includes only one pilot signal spreading circuitidentical to each of the pilot signal spreading circuits in thearrangement shown in FIG. 5. In the embodiment, pilot signals which arespread with identical codes are transmitted from the respectivetransmission antennas. Referring to FIG. 9, delay units 106-1 to 106-Nshift the transmission timings of signals from each other. Referring toFIG. 10, therefore, antennas can be identified in the receiver byseparating these signals from each other along the time axis by usingone pilot correlator 201. It is, however, difficult to accuratelyspecify reception timings corresponding to the respective transmissionantennas in an environment in which multipath waves are present.

In the systems of the embodiments described above, different spreadcodes for pilot signals are used for the respective antennas, ordifferent transmission timings of pilot signals are set for therespective transmission timings to obtain the same effect as thatobtained when different codes are used. With this operation, in thereceiver, a transmission antenna having good transmissioncharacteristics can be specified by measuring the reception power valueof each pilot signal. Thus, transmission diversity can be realized.

In each CDMA transmission/reception system described above, sincetransmission diversity using closed loop control based on thetransmitter and the receiver is realized in the FDD/CDMA scheme, adiversity effect and an interference reduction effect can be expectedusing neither a plurality of antennas nor any interference canceler in amobile station. In addition, by using transmission power control foreach user signal as well, the transmission power to a low-speed mobilestation, in which a diversity effect is remarkable, can be decreased,and interference to a high-speed mobile station can be reduced. As aresult, the overall characteristics of the system can be optimized.

What is claimed is:
 1. An FDD/CDMA transmission/reception systemcomprising: a CDMA transmitter and a CDMA receiver; a plurality oftransmission antennas included in the CDMA transmitter; a signaltransmission device coupled to the plurality of transmission antennas,the signal transmission device generating weighted transmission signalsweighted by different values and communicating the weighted transmissionsignals to the respective transmission antennas, the signal transmissiondevice further generating pilot signals and communicating the pilotsignals to the respective transmission antennas; a reception deviceincluded in the CDMA receiver, the receiving device receiving theweighted transmission signals and receiving the pilot signals from theplurality of transmission antennas of the CDMA transmitter; and anantenna control signal device coupled to the reception device, theantenna control signal device generating antenna control signalscorresponding to reception power values of the received pilot signalsand transmitting the antenna control signals to the CDMA transmitter. 2.An FDD/CDMA communication apparatus comprising: a plurality oftransmission antennas; a pilot signal transmission device generating aplurality of different pilot signals assigned to respective transmissionantennas; an antenna control signal receiving device receiving antennacontrol signals generated by a counterpart station based on thecounterpart station's reception of pilot signals; and a signaltransmission device generating transmission signals weighted by theantenna control signals so that each of said plurality of transmissionantennas is weighted by a different value.
 3. A method for transmittingand receiving CDMA communications using a plurality of transmissionantennas, the method comprising: transmitting a plurality of pilotsignals through respective transmission antennas; transmittingtransmission signals with through the respective transmission antennas;receiving the pilot and transmission signals at at least one counterpartstation; transmitting antenna control signals for controlling therespective transmitting antennas based on the power values of thereceived pilot signals from the at least one counterpart station; andweighting the transmission signals based on the control signals.
 4. Amethod for transmitting transmission signals via a plurality oftransmission antennas, the method comprising: transmitting a pluralityof different pilot signals assigned to respective transmission antennas;generating antenna control signals at a counterpart station based on thecounterpart station's reception of the pilot signals; transmitting theantenna control signals for reception by an antenna signal receivingdevice; receiving the antenna control signals at the antenna signalreceiving device; weighting the transmission signals based on theantenna control signals so that each of the plurality of transmissionantennas is weighted by a different value; and transmitting the weightedtransmission signals through the plurality of transmission antennas.